Recently, to improve performance of various safety devices such as a seat belt and an air bag, operations of the safety devices have been controlled in accordance with a weight of a passenger sitting on a vehicle seat in some cases. In the conventional passenger's weight measurement device for measuring a weight of a seated passenger, a load sensor is disposed between a vehicle floor and the vehicle seat (For example, refer to Patent Document 1 and Patent Document 2).    Patent Document 1: Japanese Patent Document 10-297334    Patent Document 2: Japanese Patent Document 11-304579
Generally, in a vehicle seat, it is often the case that a slide rail is disposed between a cushion frame and a floor, and a vehicle seat is to move in a front-and-rear (i.e., longitudinal) direction by the slide rail. Therefore, because a load transmitted to a load sensor varies according to the position of the vehicle in a longitudinal direction, the load variability according to a longitudinal position of the vehicle needs to be considered in order to improve the accuracy of the passenger's weight measurement. Although it is not a publicly know invention, the load sensor is disposed between the slide rail and the cushion frame, and the applicant of the present application filed a patent application related to such an invention (JP Application No. 2003-096855). According to such an invention, the load which is transmitted to the load sensor can be always held constant regardless of longitudinal position of the vehicle seat by moving the load sensor in a longitudinal direction in unity with the vehicle seat and the slide rail.
However, in case that the positional relation between the cushion frame and the load sensor, the positional relation between the load sensor and the slide rail, and the configuration of the cushion frame and the like are not accurate as they are designed, an initial deformation and an initial load may occur when assembling the load sensor, the cushion, and the slide rail to each other. Thus, there is a potential risk that the passenger's weight cannot be measured accurately.
An object of the present invention is to provide a passenger's weight measurement device for a vehicle seat which can be assembled to suppress the initial deformation and the initial load.